In recent times, for photographic materials, high image quality has been strongly demanded not only for small formats such as 110 size cameras and disk cameras, but also for the more conventional 35 mm type format. For increasing the image quality of color photographic light-sensitive materials, it is necessary to improve various photographic characteristics, such as the sharpness, graininess, etc., of the images, as well as color reproduction and tone reproduction.
Color photographic light-sensitive materials forming yellow images, magenta images, and cyan images in the blue-sensitive emulsion layer, the green-sensitive emulsion layer, and the red-sensitive emulsion layer, respectively, are well known. That is, by color-developing the silver halide color photographic material, the couplers in the color-sensitive emulsion layers thereof are reacted with the oxidation product of an aromatic primary amine color developing agent to form color images of azomethine dyes, indoaniline dyes, and the like. In an ordinary color negative photographic film system, the color reproduction based on a subtractive color photographic process is performed, and hence negative dye images, the colors of which are in a complementary color relation with the colors of the photographed object and the shade of which is in contrary with that of the object are formed on a color negative photographic film having the combinations of the color sensitivity and the coloring property described above. Then, by printing the negative film on a color photographic paper having similar layer structures, a color print having the correct reproductions of the colors and shade of the photographed object is obtained.
For color negative photographic films, photographic couplers, in particular, so-called DIR (development inhibitor releasing) couplers capable of releasing a development inhibitor by causing reaction with the oxidation product of a color developing agent are generally used.
A DIR coupler is a coupler having introduced into the coupling active position thereof a group which is released therefrom to show a development inhibiting action or a precursor thereof. Specific examples of such couplers are described, for example, in U.S. Pat. Nos. 3,227,554, 3,701,783, 3,615,506, 3,617,291, etc., and also improved compounds of these couplers are described in U.S. Pat. Nos. 3,933,500 and 4,477,563.
As described in the above literatures, these DIR couplers provide improvements in the sharpness of color images by edge effects as well as in the color reproduction, particularly in the degree of saturation of the pure color of blue, green and yellow as described in the aforesaid patent specifications. This effect is known as the interlayer effect or the interlayer development inhibition effect and is well known in the field of color photography. This effect is the effect that the color contrast is reduced in the case of exposing to white light than the case of exposing a monochromatic light, whereby the saturation of the monochromatic light color is increased when the gradation or the hue for white light is adjusted to a proper grey gradation as described in W. T. Hanson & C. A. Horton, Journal of the Optical Society of America. 42, pages 663 to 669 (1952) or A. Thiels, Zeitschrifts fur Wissenschaftliche Photographic. Photophysik und Photochemie. 47, pages 106 to 118 and pages 246 to 255 (1952).
As the photographic couplers, acylacetanilide series yellow couplers, pyrazolone series, pyrazolobenzimidazole series or pyrazolotriazole series magenta couplers, or naphthol series or phenol series couplers are frequently used, but the dyes formed by the coupling reaction thereof with the oxidation product of an aromatic primary amine color developing agent have undesirable side absorptions in addition to the main absorption thereof, although the extent thereof may differ, to some extent, from one dye to another. These undesirable side absorptions cause a reduction in saturation owing to the reduction in color contrast for monochromatic light in the case of establishing a proper gradation for white light.
As a technique for compensating the reduction in saturation by the undesirable absorption of the colored dyes as described above, there is known a method of using so-called colored couplers, as described, e.g., in U.S. Pat. No. 2,521,908.
On the other hand, the same effect as described above can be also obtained by applying the interlayer effect using the DIR coupler compounds disclosed in the aforesaid patent specifications.
The recent trend in increasing image quality in color photographic light-sensitive materials, and particularly the great progress in color reproduction, is largely due to making use of the interlayer effect. In particular, there has been a trend of increasing the interlayer effect in color photographic light-sensitive materials, and technical progress with respect thereto has largely contributed to the improvement of saturation.
However, in the case of reproducing color images on a color photographic light-sensitive material using color images formed on a color negative photographic film showing a large interlayer effect, color images having high saturation are obtained, but on the other hand, the following disadvantages sometimes occur. That is, in the case of photographing an object having primary colors of high purity using a color negative photographic film and then reproducing proper grey on a color photographic paper, a phenomenon occurs wherein the shade and shadow of the primary colors are not properly reproduced and gradation is lost.
The cause of the gradation loss is as follows. That is, since the saturation of, in particular, pure color is increased by the large interlayer effect as described above, (a) gradation does not exist at the high density portion on a color photographic paper, or a flattened density portion of a color photographic paper, which cannot perceive density differences is used, or, in other words, the reproduced density region of a color negative photographic film for pure color corresponds to the portion shifted from the reproduced exposure amount region of a color photographic paper to a high exposure amount side. Furthermore, (b) owing to an increased satuaration, the complementary color for the pure color is not printed on a color photographic paper and the shade is not reproduced or, in other words as above, the reproduced density region of a color negative photographic film corresponds to the portion shifted from the reproduced exposure amount region of a color photographic paper to a low exposure amount side.
This is explained further based on the following practical example. When a clear red and blue object which is shaded is photographed using a color negative photographic film having a large development inhibiting effect for a red-sensitive emulsion layer provided from other silver halide emulsion layers and a large development inhibiting effect for other silver halide emulsion layers provided from the red-sensitive emulsion layer, or a color negative photographic film having a large development inhibiting effect for a blue-sensitive emulsion layer provided from other silver halide emulsion layer and a large development inhibiting effect for other silver halide emulsion layers provided from the blue-sensitive emulsion layer, there occur the following phenomena. In the former case, the saturation is increased, caused by the large inhibiting effect provided from other emulsion layers; that is, cyan is reluctant to be reproduced in the color print obtained, and the saturation is also increased by the large inhibiting effect provided to other emulsion layers, and thus magenta and yellow are liable to be reproduced in the color print obtained to provide clear red. Similarly, in the latter case, yellow is reluctant to be reproduced in the color print and the saturation is increased, and cyan and magenta are liable to be reproduced to increase the saturation of blue. However, if the aforesaid development inhibiting effect of color print, that is, the interlayer effect is further increased, the saturation of magenta and yellow for a red object is too high to reproduce the shade thereof as well as cyan is not reproduced in the color print and the delicate shadow in red cannot be reproduced. Also, the saturation of cyan and magenta for a blue object is too high to reproduce the shade as well as yellow is not reproduced in the color print and the shadow cannot be reproduced. The above-described explanation is applicable not only for a red or blue object, but also by analogy for a green or yellow object.
The phenomenon that a shade or shadow is not reproduced and gradation is lost is specific to an object of primary color having high saturation and also is specific to a color photographic light-sensitive material having large interlayer effect.
Considering the importance of the interlayer effect as a recent technique for increasing image quality of color photographic light-sensitive materials, it is very desirable to eliminate such "gradation loss" phenomenon.
For avoiding the occurrence of "gradation loss" phenomenon, various means, such as that the interlayer effect itself is reduced, the spectral sensitization distribution of a photographic light-sensitive material is changed, and coloring materials are mixed that have hitherto been known, but such means are all accompanied by a reduction in saturation. Accordingly, it has been desired to develop a means for eliminating the foregoing disadvantages without reducing the merit of avoiding the occurrence of "gradation loss" phenomenon.